1. The Field of the Invention
This invention relates generally to electrical devices for tracking items in the possession of a person, and more particularly to a system in which a first electrical device can selectively communicate with at least one other electrical device and can indicate a presence and/or location of the other device.
2. The Backaround Art
Various devices are known in the art for monitoring or locating objects that are commonly found in possession of a person. For example, in U.S. Pat. No. 5,680,105 a lost object locator includes activation units that are mounted on a rack and response units that are attached to objects that are commonly misplaced such as car keys. Each of the activation units corresponds to a single response unit and when one of the objects that has a response unit attached thereto is lost or misplaced, the corresponding activation unit can be activated to send a signal to the response unit on the lost object. When the response unit attached to the lost object receives the signal from the activation unit, an audible tone is emitted from the response unit which, ideally, will indicate the location of the lost object to the person activating the activation unit. The invention also provides for mobile activation units that can be placed in areas that the person believes are nearer the lost object so that the audible tone can be easily detected by the person when the response unit is activated by the activating unit. Undesirably, however, an activation unit is required for each object that is to be located and the activation unit provides only a single function for locating the lost object. Further, although the lost object locator provides for a master activation unit that can be detached from the rack when a person is looking for lost objects, the master activation unit suffers from a lack of programmability and individual control for interacting with objects. For example, the master activation unit is incapable of selectively activating individual response units. Finally, the response units are incapable of locating a lost or misplaced activation unit.
Another device for monitoring or locating objects is the child proximity detector disclosed in U.S. Pat. No. 5,646,593. The child proximity detector includes a parent unit that receives pulse signals on a regular interval from a child unit. When the parent unit fails to receive a signal from the child unit, an alarm condition is established in the parent unit. Because these detectors can be xe2x80x9cfooledxe2x80x9d by causing a parent unit to fail to reach an alarm state when the child unit is out of range, those skilled in the art have developed parent and child units that communicate with each other. However, even these improved xe2x80x9cintelligentxe2x80x9d units suffer from the disadvantage of having limited functionality because a person cannot dynamically modify a parent unit to implement individual control over a single child unit, e.g., the units can not be programmed to selectively activate a single child unit. Furthermore, the child unit cannot be used to locate the parent unit.
Yet another device of the prior art disclosed in U.S. Pat. No. 5,621,388 provides the function of a child proximity detector by monitoring a person, or persons, to determine if they have moved, or been moved, further than a preselected distance from a base station. Although this device provides dual functionality in the parent device of both monitoring and locating a person wearing a remote (i.e., child) device, the device has drawbacks for use as a possession tracker because it does not offer more than two functions. One drawback of only having dual functionality is that the system will not operate in a locating mode unless the remote device is located outside the preselected distance set in the parent device. The prior art device also lacks the ability to selectively activate remote devices with the parent device. In addition, this prior art device does not have the capability to automatically detect when it should shut down to avoid interfering with other signals, e.g., when it is near a transponder on a commercial airline during take off. Further, the remote device will not operate in a manner to locate the parent device.
In view of the foregoing, it would be advantageous to provide a system having a local (i.e., parent) device that can be selectively programmed by a person to track one or more remote (i.e., child) devices, wherein the remote device can also operate to locate the local device, and wherein the system will automatically detect when communication signals between the devices should not occur and thus shut down communications.
It is an object of the present invention to provide a system for monitoring when a selected object is no longer within a preselected distance of a person.
It is a primary object of the present invention to provide a system for locating a selected object that has been misplaced.
It is another object of the invention to provide such a system for automatically detecting when communication signals between the electrical devices of the invention should cease due to interference with external communication signals.
It is also an object of the invention to provide such a system for locating a parent device with a child device.
It is a further object of the invention to provide such a system for locating a child device with a parent device.
The above objects and others not specifically recited are realized through a system for selectively detecting the presence of a plurality of objects in proximity to a person. The system includes a plurality of child units each having a first communicating device (such as a transceiver) for sending a locator signal and for receiving a control signal. Further, the system includes a parent unit having a second communicating device for receiving the locator signal from at least one of the plurality of child units, electronic means, such as a processor, microprocessor, analog circuitry, or other electrical devices known in the art, for monitoring the at least one child unit and for determining whether the child unit is within a preselected range, at least one alarm for signaling the person when the selected child unit is outside, the preselected range, and controls for selectively controlling the child units to be monitored and for controlling activation of the child units.
In a preferred embodiment, the system includes global positioning devices associated with each of the parent units and child units for determining relative positions of the parent and child units. In another preferred embodiment, the controls are capable of controlling activation of the child units and allow a user to add or eliminate child units that the user would like monitored.
In yet another preferred embodiment in accordance with the present invention, the parent device can automatically detect external communication devices that require the parent device to cease communicating with one or more child devices and thus will automatically shut down when such external devices are detected. An electronic timer may also be included such that the parent device automatically reestablishes communications with the child devices after a preselected time period.
In still another preferred embodiment, the child device can be controlled to independently locate the parent device.
In another preferred embodiment, the parent unit includes a tracking mechanism for assisting a user in locating one or more of the child units. The tracking mechanism may include global positioning devices or various devices that can detect the strength of a signal transmitted by a child unit. Preferably, the tracking mechanism includes a display that indicates the proximity to a particular child unit.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the present invention. The objects and advantages of the invention may be realized and obtained by means of the instruments and combinations particularly claimed in the appended claims.